Automatic telephone system



Nov. 12, 1929. c. E. LOMAX AUTOMATIC TELEPHONE SYSTEM Original Filed April 16, 1927 3 Sheets-Sheet l u h h u l w M .R

a [I I U A n n u l \MNVILFIMIL 3 IW PL --TnuEnZur- .EZarence ELamax Nov. 12, 1929. c. E. LOMAX AUTOMATIC TELEPHONE SYSTEM Original Filed April 16, 1927 3 Sheets-Sheet 2 Inusn Dr Ilaranca E;Lnmsx WM C. E. LOMAX AUTOMATIC TELEPHONE SYSTEM Nov. 12, 1929.

3 Sheets-Sheet 3 I Original Filed April 16, 1927 Ilarsnca E. Lcmiax Patented Nov. 12, 1929 UNITED STATES PATENT? OFFICE CLARENCE E. LOMAX, 01 OAK PARK, ILLINOIS, ASSIGNOB TO RESERVE HOLDING COH- PANY, OF KANSAS CITY, MISSOURI, CORPORATION OF DELAWARE AUTOMATIC TELEPHONE SYSTEM Application filed Aprl116, 192?, Serial No. 184,197. Renewed January 12, 1929.

The present invention relates to automatic telephone systems in general, but is concerned more particularly with the circuit arrangements of an improved two-way trunk circuit for use in connecting two automatic exchanges.

The principal object of the invention is to eliminate the noise from the talking circuit ofaninter-exchange trunk line which is subject to inductive interference or disturbances from high tension circuits or other high powered circuits. This is accomplished by removing the battery and ground connections from the talking conductors of the trunk line when the called party answers.

According to a feature of the invention, the called party is fed talking battery from the local connector on local calls and on interoifice calls the battery at the connector is disconnected and the called party is fed talking battery from the repeater.

Another feature of the invention relate to the novel circuit arrangements by means of which. the calling subscriber controls the release of the automatic switches in the distant exchange. a I

Another feature of the invention consists in the provision of an improved automatic switch for use in private automatic exchanges,

the switch being of a type which is commonly known as a switching through connector.

The foregoing and other improvements will be described fully hereinafter, reference being had to the accompanying drawings.

Referring to the drawings, comprising Figs. 1, 2, and 3, there is shown by means of the usual circuit diagrams suificient of the apparatus in the systemic enable the invention to be explained and understood.

In Fig. 1 there is shown at A an automatic substation of a well known type. The line of substation A terminates in the usual manner in connector bank contacts and an indi vidual rotary lineswitch such as indicated b reference character LS. The lineswitch L is of the well known rotary type in which the Wipers have no normal position and which have access to selector switches such as indicated b the reference character S. The selector is of the well known vertical and Incoming calls from the distant automatic exchange extend over conductors such as conductors 30 and 31 to incoming repeaters such as repeater IR. Repeater IR is similar to the repeater IR? in Fig. 2. Associated with each incoming repeater IR there is shown an incoming selector switch IS which is of the well known vertical and rotary type of Strowger switch. The incoming selector switch IS has access to the connectors such as C. The bank contacts of the incoming selectors are multipled with the bank contacts of the first selectors such as S.

In Fig. 2 the trunk line comprising the conductors 30 and 31 terminates in the distance automatic exchange in the repeater 0B which is similar to the repeater OR in Fig. l and also in the incoming repeater IR which is similar to the incoming repeater IR in Fig. 1. The outgoing repeater ()R is used for extending outgoing calls while the incoming repeater IE is used only for incoming calls. A number of relays are shown in the incoming repeater IE the circuit arrangement of which permits certain novel operating features to be performed. Associated with the incoming repeater IR there is shown an incoming selector IS which has access to connectors such as connector C Fig. 3. The connector C is a vertical and rotary switch of the well known Strowger type so far as mechanical construction is concerned, the circuits of which, however, have been somewhat improved as will appear more clearly hereinafter. The connector C is also accessible from the first selectors such as S and is also used for completing local connections. The

connector has access to automatic subscribers such as shown at substation A The substation A is similar to substation A and is of the well known automatic type having the usual calling device, talking 1nstrumentalities. and ringer. The line of substation A terminates in an individual rotary line'switch LS which is of the well known r0- tary type. The lineswit-ch LS is simllar to the lineswitch LSFin Fig. 1 and has access to first selectors such as selector S The selector S is similar to the selector S in Fi 1 and has access to the outgoing repeaters R and the connectors such as connector C Having described the apparatus involved the operation of the same will now be ex plained more in detail. For this purpose it will be as sumed that the subscriber at substation A, Fig. 1, desires to establish a connection with the subscriber at substation A Fig. 3. When the receiver is removed at substation A a circuit is closed over the line for the line relay. of the lineswitch LS whereupon the lineswitch, in a well known manner, selects an idle trunk extending to a selector. It will further be assumed that the selector S is the selector seized by thelineswitch LS and that the subscriber at substation A, by the operation of his calling device, operates the selector S to the group of bank contacts in which the outgoing trunks to the desired exchange terminate and that the selector S seizes the outgoing repeater 0R The selector S in switching through in the well known manner, closes a circuit for energizing the line relay 6 of the repeater 0R over the subscribers loop. The circuit may be traced as follows: from ground, by way of the lower winding of line relay 6, lower left-hand winding of the repeating coil, bank contact 23, the subscribers loop including the wipers of the line switch LS and selector S bank contact 21, upper left-hand winding of the repeating coil, to the upper winding of line relay6 and battery. At armature 14 relay 6 closes a circuit for energizing slow-to-release relay 7 The latter relay energizes and at armature 15 causes slow-to-release relay 9 to energize. At armature 16 relay 7 opens the circut of relay 8 and at armature 17 prepares a .circuit for series relay 5. Relay 9, upon energizing, at

armature 19 grounds the release trunk con:

ductors 24 thereby maintaining the selector S and lineswitch LS in operated position and 'at the same time guards the outgoing repeater 0R from seizure by other selectors in the well known manner. At armatures 18 and 20 the trunk conductors 30 and 31 are disconnected from the incoming repeater IE and are connected instead to the right-hand winding of the repeating coil. When the trunk conductors 30 and 31 are connected to the right-hand windings of the repeating coil in the repeater CR a circuit may be traced for energizing the line relay 47 of the incoming repeater IR as follows: from ground, by way of the lower winding of line relay 47, armature 55, lower left-hand winding of the repeating coil, conductor 41, armature 20', conductor 31, armature 20, lower and upper-right hand windings of the repeating coil, armature 13, armature 18, conductor 30, armature 18, conductor 40, upper left-hand winding of the repeating coil, armature 54, to the upper winding of line relay 47 and battery. Line relay 47, upon energizing, at armature 57 closes a circuit for energizing release relay 48 and at armature 56 closes a circuit for energizing series relay 50 and the line relay of the incoming selector 1S as follows: ground by way of armature 63, armature 56, series relay 50, back contact and armature 01 the switching relay in the selector 18 to the upper winding of the line relay of the selector and battery. At armature 58 relay 48 grounds the release trunk conductor 2 1 therey guarding the outgoing repeater 0R from seizure by selector switches such as selector S Fig. 3. Relay 50, upon energizing, closes a circuit for energizing relay 51 and the latter relay prepares a circuit for relay 52. The outgoing repeater 0R the incoming repeater IE and the incoming selector 1S are now in readiness to receive the impulses of the next digit of the called number.

Responsive to the operation of the subscribers' calling device the circuit of the line relay 6 is interrupted a plurality of times whereby said relay is deenergized a corresponding number of times. Upon the first deenergization of relay 6 a circuit is closed for energizing relay 5 at armature 14. Relay 5 is energized and at armatures 10, 11, and 12 shorts out both windings of the repeating coil in orderto improve the impulsing circuit. -Both relays 5 and 7 are slow acting and therefore maintain their armatures attracted during impulsing. At armature 13 line relay 6 opens the bridge across the trunk conductors 30 and 31 thereby opening the cirguRit of line relay 47 of the incoming repeater Each time the line relay 6 of the repeater 0R interrupts the bridge across the trunk conductors 30 and 31 at armature 13 of the line relay 47 of the incoming repeater R is deenergized. The latter relay at armature 56 interrupts the circuit of the line relay of the selector 1S alike number of times whereupon said selector is operated in the vertical direction in the well known manner to select the desired group of trunk lines extending to the proper group of connectors. The incoming selector 1S now rotates in the well known manner to select an idle connector in the selected group. It will now be assumed that the connector C shown in Fig. 3 is the connector seized by the incoming selector 1S The seized connector C is made busy to selector switches such as selectors 1S and S from ground at armature 58 which extends through the incoming selector 18 to wiper 64 and thence by way of bank contact 67 to conductors 70 and 170 and multiples thereof. When the selector 1S seizes the connector C the switching relay in the selector IS closes a circuit for the line relay 100 ot the'connector C as follows: ground by way of armature 63, armature 56, series relay 50, the upper talking conductor of the selector 1S wiper 63, bank contact 66, conductor 69, armature 115, and upper winding of line relay 100 to battery. Theline relay energizes over the above traced circuit and closes an energizing circuit for release relay 101. Release relay 101, upon energizing, at armature 113closes a circuit for short circuiting the lower windingof relay 106, said short circuit including the-grounded release trunk conductor 70. At armature 114 release relay 101 opens a pointin the circuit of the release magnet 110 and prepares a circuit for the series relay 102 and the vertical magnet. The connector C isnow ready to receive the impulses of the next digit of the called number.

When the calling subscriber at substation A operates his calling device inaccordance with the next digit of the called number the impulses are repeated from the outgoing repeater OR to the incoming repeater IR in the same manner as previously described. Line relay 47 in the repeater 1R now interrupts the circuit of the line relay 100 of the connector C whereupon said relay deenergizes for each impulse. Release relay 101 being slow acting does not release during impulses and therefore a circuit may be traced for the series relay and vertical magnet when the line relay 100 deenergizeson the first impulse: ground by way of the armature.of line relay 100 and its resting contact, armature 114, and its working con-,

tact, normally closed off normal springs 150, series relay 102, and vertical magnet 109 to battery. Upon the first vertical movement of the switch the off-normal springs 150 are shifted and the remaining impulses to the series relay and vertical magnet are transmitted over a new circuit which includes the normally open oif-normal contacts and the armature and working Contact of relay 102. Relay 102 being a slow-acting relay maintains its circuit intact during impulses. By the operation of the vertical magnet 109 the switch wipers 141, 142, and 143 are raised step by step and are finally brought to rest opposite the level in which the line of substation A is terminated. 'At the end of the vertical movement relay 102 deenergizes and transfers the impulsing circuit to the rotary magnet 111.

The calling subscriber may now call the next and last digit in the desired number. As before, a series of interruptions are repeated to the line relay 100 and the line relay tated step by step and are finally brought to rest 1n engagement with the particular set of contacts in which the line of substation A is terminated, these contacts being indicated in the drawing by reference characters 144, 145, and 146. The slow-acting series relay 107 is energized in series with the rotary magnet and maintains its armatures at tracted throughout the rotary movement. At armature 132 the series relay 107 opens the circuit of the switching relay 108 and prepares a circuit including the busy relay 105 for testing the called line and at armature 133 maintains its own circuit and the circuit of the rotary magnet 111 independent of armature 125. The operation of the connector 0 now depends upon whether the called line is busy or not. I

It will now be assumed that the line of substation A is busy when called. Under these circumstances there will be a ground poten tial upon the test contact 145 and when the test wiper 142 comes to rest in engagement therewith the busy relay 105 will be energized over a circuit as follows: ground on the test contact 145, test wiper 142, armature 132 and its working contact, resistance 180, armature 121, and winding of busy relay 105 to battery. Shortly after the impulses cease the slow-acting series relay 107 deenergizes and completes-a locking circuit for the busy re- 7 lay as follows: ground by way of grounded release trunk conductor 70 low resistance winding otrelay 106, armature 124 and its working contact, normally closed springs controlled b armature 132, and thence over the previous y traced circuit to the upperwinding of busy relay 105. It may be mentioned at this time that the resistance 180 in the above locking circuit is of such resistance as to maintain the busy relay 105 energized but is too high to permit relay 106 to energize. In addition relay 106 is still short circuited from ground at armature 113. At armature 125 the busy relay opens the circuit of the rotary magnet 111 and'at armature 126 closes mature 115.

When the armature 115 opens the circuit of line relay 100, it also opens the circuit of series relay 50 in the incoming repeater 1R whereupon the latter relay deenergizes. Relay 50, upon deenergizing, closes a circuit for energizing switching relay 52 whereupon said relay energizes and closes a locking circuit for itself which includes the grounded armature 58. At arlnatures 60 and 62 relay 52 connects the talking conductors 42 and 43 of the incoming repeater IE to the talking conductors 69 and of the connectorC and at armature 63 disconnects ground from armature 56.

Returning now to the connector G a circuit may now be traced for transmitting an' audible busy signal to the calling subscriber. The busy signalling circuit includes the armature 127 of the busy relay 105, armature 130, armature 123, lower talking condenser, talkin conductor 71, the right-hand windings 0? repeating coils in repeater 1R armature 60, to ground at armature 56. By means of the repeating coils the calling subscriber is given the busy tone in the Well known manner.

' When the calling subscriber hears the well known busy tone, he will replace his receiver thereby opening the circuit of the line relay 6. At armature 13 relay 6 opens the bridge across the trunk and at armature 14 opens the circuit of release relay 7 whereupon the latter relay deenergizes. At armature 15 the circuit of relay 9 is opened and said relay releases. Due to relays 7 and 9 being slow acting, relay 9 does not deenergize and remove the guarding'ground from release trunk conductor 24 until a considerable time after the bridge across the conductors 30 and 31 is opened at armature 13. This arrangement is provided to prevent the seizure of the trunk line until all the apparatus in both exchanges has had sufficient time to release. By the removal of ground from conductor 24 the lineswitch LS and selector S are released in the well known manner.

When the bridge across the trunk is opened at armature 13 line relay 47 in the incoming repeater 1R deenergizes and opens the circuit of release relay 48 whereupon the latter relay deenergizes. At armature 58 release relay 48 opens the locking circuit of relay 52 whereupon the latter relay deenergizes. At armature 58 relay 48 also removes ground from release trunk conductors 24 and 70 whereupon the incoming selector is released in the well known manner and the circuits of the busy relay 105 and relay 103 are opened. Busy relay 105 and relay 103 deenergize and the latter relay at armature 117 closes an energizing circuit for the release magnet 110 whereupon the connector is released in the well known manner. All the apparatus used in extending the connection is now in normal position and may be used for other calls.

Having explained what occurs when the called line is busy, it will now be assumed that the called line is idle. Such being the case, when the test Wiper 142 comes to rest in engagement with the v test contact 145, it Wlll find no ground potential and the busy relay 105 will not be energized. Instead, when the slow acting relay 107 falls back, a circuit is closed through the upper winding of the switching relay 108 as follows: from ground by way of armature'113, armature 124 and its resting contact, upper winding of switching relay 108, armature 132, test wiper 142, test contact 145, conductor 147, and winding of the cut-01f relay of the lineswitch LS to battery. Upon the closure of the above traced circuit the cut-oii relay of the line switch LS is operated to clear the line of substation A from its normal battery and ground connection in the lineswitch LS This is accomplished by the well known me chanical interlocking arrangement of the rotary lineswitch LS In the connector C, when the switching relay 108 is energized it closes a locking circuit for itself which includes the lower winding, armatures 137 and 136 and the grounded release trunk conduetor 70. In addition armature 136 connects the grounded release trunk conductor 70 to the test wiper 142 thereby connecting a guard ing potential to test contact 145 and multiples thereof. At armature 138 relay 108 opens the circuit of relay 107 and rotary magnet 111 and at armature 139 completes a circuit for energizing relay 103. The circuit for energizing relay 103 includes the grounded release trunk conductor 70, armature 129, armature 134, armature 139, and the winding of said relay. At armatures 135 and 140 switching relay 108 connects interrupted generator to the called line.

Before proceeding with the ringing opera tion it should be mentioned that relay 103 upon energizing opens the circuit of the line relay 100 at armature 115 and at armature 117 opens a point in the circuit of the release magnet 110 so that that magnet will not be energized when the line and release relays shortly deenergize. At armature 115 relay 103 also opens the circuit of relay 50 which thereupon deenergizes and causes the relay 52 to energize and lock in the same manner as previously described. The release of relays 100 and 101 are without eilect at this time other than to prepare the release circuit which is now open at armature 117.

The connection to the desired line has now been completed and ringing current from the generator, Int. Gen, is intermittently projected out over the line to operate the ringer at the substation A. The ringing circuit may be traced as follows: from ground by way of llii armature 122, armature 140, wiper 143, contact 146, the bridged ringer and condenser at the substation A, bank contact 144, wiper 141, armature 135. armature 119, lower winding otring cut-oft relay 104, to interrupted generator Int. Gen. The ringing current passing through the lower winding of ring cut-oii' relay104 induces a current in the upper winding of said relay which forms a circuit through the lower winding of busy relay 105, armature 123, lower talking condenser, through the lower talking conductor of the connector over the previously traced busy signalling circuit to ground at armature 56, for transmitting the well known ring back tone to the calling subscriber each time the called partys bell is rung.

lVhen the called party answers the ring cut-off relay 104 energizes and at armature 120 completes a locking circuit for itself which includes the groundedrelease trunk conductor 70. Ring cut-ofi relay at armature 123 opens the ring back circuit and at armatures 119 and 122 opens the ringing circuit. At the same armatures relay 104 connects the talking conductors of the called line straight through to the talking conductors of the incoming repeater 1R independent of any ground or battery connections at the connector C lVhen the line of the called subscriber A is connected through to the incoming repeater 1B the back bridge relay 45 in the incoming repeater IR is energized and said relay closes a circuit by way of armature 59 for energizing relay 46. Relay 46, upon energizing, at armature 53 closes a circuit for energizing relay 49 and the latter relay connects ground to the release trunk conductor 24 so as to maintain ground on said conductor after relay 48 deenergizes which it does shortly hereafter. At armatures 54 and 55 and their resting contacts relay 46 opens the circuit of line relay 47 thereby removing all battery and ground connections from the inter-office trunk, and at armature 55 and its working contact substi tutes a high resistance bridge for the battery and ground connections of the line relay. The line relay 47 deenergizes and also causes release relay 48 to deenergize and open the original energizing circuit of relay 46 at armature 59, but the latter relay is maintained energized by way of resistance 44 which is connected in shunt of armature 59. By the removal of battery and ground from the inter-oilice trunk the inductive disturbances caused by close high tension circuits is eliminated thereby rendering an eificient talking circuit over a trunk line which otherwise would be very poor on account of the inductive disturbances. The connection now having been completed the calling and called subscribers may converse with each other as desired. 4

After conversation and responsive to the replacement of the receiver by the calling subscriber at substation A the circuit of line relay 6 is openedand said relay and releasev relay 7 deenergize. Shortly after release relay 7 deenergizes relay 9 also deenergizes and removes the guarding ground atarmature 19 so as to render the inter ofiice trunk selectable. It will be noted that this ground 15 maintained for an interval in order to allow all the apparatus which is connected to the trunk to be properly released before it can again be selected. By the removal of ground from the release trunk the selector S and the lineswitch LS are released in the well known manner. y

When release relay 7 deenergizes a circuit may be traced through the upper winding of differential relay 46 as follows: ground by way of armature 14 and its resting contact, armature 17 and its resting contact, armature 20, conductor 31 armature 20, conductor 41, lower left-hand winding of the repeating coil, armature 55 and its working contact, upper winding ofdifierential relay 46, upper left-hand winding of the repeating coil, conductor 40, armature 18', conductor 30, armature 18, armature 16, and winding of relay 8 to battery. Relay 46 immediately deenergizes because the'direction of current flow in the upper winding of relay 46 is in opposition to that through its lower winding. It should be explained that resistance 44 is high enough to prevent relay 46 from again energizing when relay 9, Fig. 1, falls back. Relay 46, upon deenergizing, at armature 53 opens the circuit of relay 49 whereupon the latter relay deenergizes and removes ground fromrelease trunk conductor 24 thereby opening the circuits of relays 103, 104, and 108 and permitting the selector IS and connector C to release in the manner as previously described. All the apparatus in the originating exchange is now in normal'condition and may be used for extending other calls.

In case the called subscriber atsubstation A is the first to replace'his receiver the circuit of relay 45 in the incoming repeater R is opened and said relay releases and opens the circuit of relay 46. Relay 46, upon releasing, at armature 53 opens the circuit of relay 49 whereupon said relay releases and removes ground from the release trunk 24'. However, before said ground is removed line relay 47 is again energized over the trunk line and release relay 48 again applies ground at armature 58 to release trunk conductor 24 thereby maintaining the selector IS and connector C in operated position. If the calling subscriber should replace his receiver under the above conditions the circuit of the line and release relays would be opened in an obvious manner and the switches returned to their, normal positions.

The automatic subscriber at substation A may call the automatic subscriber at substa- 'tion A, 1, in the same manner as just previously explained with the exception that the lineswitch LS the selector S the outgoing repeater 0R which is identical to the outgoing repeater 0R the incoming repeater 1B which is identical to the repeater IR, the incoming selector 1S and the connector C which is identical to connector C is used for extending and completing the call to the subscriber at substation A.

Having described how inter-exchange calls are completed a description will now be given of the apparatus used in completing local calls. For this purpose it will be assumed that an automatic subscriber in the same exchange as substation A desires a connection with the subscriber at A. The calling subscribers lineswitch is operated in the well known manner responsive to the removal of the receiver and by the operation of his calling device the calling subscriber causes the first selector to seize an idle connector which has access to the line of the desired subscriber or substation A It will further be assumed that the selector has seized the connector C over the conductors 169, 170, and 171. When the selector seizes the connector C the line relay 100 and release relay 101 energize in the manner previously described and the latter relay at armature 113 prepares the circuit for relay 106. Due to ground being momentarily sent forward over conductor 1-70 from'the selector S relay 106 is not at this time energized. However, when the release relay of the selector deenergizes after the selector switches through in the well known manner ground will be removed from conductor 170 whereupon a circuit may be traced from ground at armature 113, lower winding of relay 106, release trunk conductor 170, wiper of the selector, and through the winding of the switching relay to battery over the well known circuit. Relay 106 energizes over this circuit and the switchingrelay is maintained in energized position. At armature 128 relay 106 completes a locking circuit for itself and at armature 129 and its working contact shunts out the lower winding thereby making said relay slow to release and at armature 129 and its resting contact opens the circuit of relay 103. By the above circuit operations just described the circuits of the connector C? arenow arranged to work as a-local connector and not as a switching through connector. The operation of the connector is now the same as previously described with the exception of course, that relay 103 is not energized and therefore the line relay 100 is not disconnected. The line relay 100 feeds talking battery to the calling party. Talking battery for the called subscriber extends through the two windings of the busy relay as follows ground at armature 113, working contact of armlature 129 and said armature, armature 120, lower winding of busy relay 105, normallyclosed springs 7 'cut-ofi relay. It will be noted that the busy relay 105 provides for giving the calling subscriber a busytone and controls the switching through relay in case the line called is busy, is also included in the circuit for giving the calling subscriber a ring back tone when the'called party is being rung, and also acts as the battery feed relay for feeding talking battery to the called subscriber on local calls.

The calling and called subscriber may now converse with each other as desired. When conversation is finished the replacement of the receiver by the called party is without eiiect. When the calling subscriber replaces his receiver the line and release relays 100 and 101, respectively, deenergize. The latter relay at armature 113 removes the locking ground whereupon the ring cut-ofi relay 10 1, relay 106 and switching relay 108 deenergize. At armature 11 1, release relay 101 completes a circuit for energizing the release magnet 110, whereupon the connector 0 releases in the well known manner. The lineswitch of the calling subscriber and the selector are also released in the well known manner and all the apparatus included in establishing the connection is now returned to normal position.

Having described my invention, what I consider to be new and desire to have protected by Letters Patent will be pointed out in the appended claims. i

. What is claimed is:

1. In a telephone system, two exchanges, a two-way trunk line comprising only two conductors connecting said exchanges, said trunk line terminating in an incoming repeater andan outgoing repeater in each exchange, means for seizing the outgoing repeater in one exchange, means in said outgoing repeater for repeating impulses over the two conductors of said trunk line in serie to the incoming repeater in the second exchange, a line relay in said incoming repeater having two windings through the medium of which operating current is normally connected to said trunk conductors, a utomatic switches in the second exchange, contacts on said line relay for repeating the impulses sent over said trunk line-to operate said switches to complete a connection, and means controlled by the response of the called subscriber for disconnecting said line relay and all battery connections from said trunk line during conversation.

2. In atelephone system, two exchanges, a two-way trunk line'comprising only two conductors connecting said exchanges, said trunk line terminating in an incoming repeater and an outgoing repeater in each exchange, means for seizing the outgoing repeater in one exchange, means in said outgoing repeater for repeating impulses over the 'two conductors of said trunk line in series to the incoming repeater in the second exchange, a line relay in said incoming re peater having two windings through the medium of which operating current is normally connected to said trunk conductors, automatic switches in the second exchange, contacts on said line relay for repeating the impulses sent over said trunk line to operate said switches to complete a connection, means controlled by the response of the called subscriber for disconnecting said line relay and all battery connections from said trunk line during conversation, and means independent of control from said line relay and the called subscriber for maintaining said switches in operated position. v

3. In a telephone system, two exchanges, a two-way trunk line comprising only two conductors connecting said exchanges, said trunk line terminating in an incoming repeater and an outgoing repeater in each exchange, m'eans for'seizing the outgoing repeater in one exchange, means in said outgoing repeater for repeating impulses over the two conductors of said trunk line in series to the incoming repeater in the second exchange, aline relay in said incoming repeater having two windings through the medium of which operating current is normally connected to said trunk conductors, automatic switches in the second exchange, contacts on said line relay for repeating the impulses sent over said trunk line to operate said switches to complete a connection, a back-bridge relay in said incoming repeater operated by the response of the calledsubscriber, said back-bridge relay feeding talking battery to the called subscriber, and means controlled by said last mentioned relay for disconnecting said line relay and all'battery connections from said trunk line during conversation and for maintaining said switches in operated position independent of said line and back-bridge relays and the called subscriber.

4. In a telephone system, two exchanges, a two-way trunk line comprising only two conductors connecting said exchanges, said trunk line terminating in an incoming repeater and an outgoing repeater in each exchange, means for seizing. the outgoing repeater in one exchange, means in said outgoing repeater for repeatingimpulses over the two conductors of said trunk line in series to the incoming "called subscriber, said back-bridge relay feed ing talking batteryto the called subscriber, means controlled by said last mentioned relay for disconnecting said line relay and all battery connections from said trunk line dur- 1'ng:conversation and for m'aint'aining said switches in operated position independent of said line and back-bridge relaysand the called subscriber, and means controlled from said outgoing repeater for releasing said switches.

5. In a telephone system, two exchanges, a two-way trunk line comprising only two conductors for connecting said exchanges, means for seizing said trunk line at one exchange, an impulsing circuit including the two conductors of said trunk, the two windings of a line relayat the second exchange and battery and ground connections in series, auto matic switches in the second exchange controlled by said impulse circuit to complete a connection, a talking circuit including the two conductors of said trunk line but excluding all battery and ground connections, and means controlled by the response of the called subscriber for automatically switching the two conductors of the trunk line from the impulsing circuit to the talking circuit.

6. In a telephone system, two exchanges, a two-way trunk line comprising only two conductors for connecting said exchanges, means for seizing said trunk line at oneexchange, an impulsing circuit including the two conductors of said trunk, the two wind ings of a line relay at the second exchange and battery and ground connections in series, automatic switches in the second exchange controlled by said impulse circuit to complete a connection, a talking circuit including the two conductors of said trunk line but excluding all battery and ground connections, means controlled by the response of the called subscriber for automatically switching the two conductors of the trunk line from the impulsing circuit to the talking circuit, and means for feeding talking battery to the called subscriber over the talking conductors of said switches from a point between said trunk line and said switches.

7. In a telephone system, two exchanges, a two-way trunk line comprising only two conductors connecting said exchanges, said trunk line terminating in an outgoing repeater in one exchange and an incoming repeater at the other exchange, means for seizing said outgoing repeater, a line relay in said incoming repeater having two windings through the medium of which operatingcurrent is normally connected to the conductors of said trunk line, an impulsing circuit including the windings of said relay and the conductors of said trunk line in series, a talking circuit including the conductors of said trunk line but excluding said line relay and all battery connections, automatic switches,

men ns controlled by said line relay for operating said switches to complete a connection, and means controlled bythe response of the called subscriber for automatically switching the conductors of said trunk line from said impulsing circuit to said talking circuit.

8. In a telephone system a local exchange, a distant exchange, a called line, a connector switch having a pair of talking conductors and a release trunk conductor, means including said connector for completing connections to said line from either said local exchange or said distant exchange, a line relay in said connector for feeding talking battery to a calling line on local connections, a busy relay in said connector for feeding talking battery to the called line on local connections, a switching relay in said connector when energized for switching the talking conductors of said connector straight through excluding all battery feed connections from said line and busy relays, a control relay permanently connected to the release trunk conductor of said connector which when energized renders said switching relay inoperative, means automatically controlled over said release trunk conductor for energizing said control relay on local calls and for short circuiting said control relay on inter exchange calls to render the same inoperative, and means independent of said connector for feeding talking battery to the called line on inter-exchange calls.

9. In an automatic telephone system, a calling subscribers line and a called subscribcrs line, subscriber controlled means including a repeater for use in setting up a connection between said subscribers lines, said repeater feeding operating battery toward only the calling subscribers line during the setting-up of the connection, means in said repeater operative responsive to the completion of the connection to the called subscribers line for feeding talking battery to the called subscribersline, and means in said repeater controlled by the response of the called subscriber for disconnecting said operating battery extending toward the calling subscribers line.

10. In an automatic telephone system, a calling subscribers line and a called subscribers line, subscriber controlled means including a repeater for use in setting up a connection between said lines, said repeater feeding operating battery toward the calling line but not the called line during the setting up of the connection, a double wound relay in said repeater, means in said repeater operated responsive to the completion of the connection to the called subscribers line for feeding talking battery to the called .sub-

scribers line throughthe windings of said relay, said relay energized by the response otthe called subscriber, and means in said repeater controlled by said relay for disconnecting said operating battery extending toward the calling subscribers line.

11. In an automatic telephone system, a temporarily established connection including a trunk line, a repeater, and automatic switches, a differential relay in said repeater normally connecting battery and ground to the talking conductors of said trunk line, means for energizing said relay to disconnect the battery and ground connections from said trunk line, and means controlled over the talking conductors of said trunk for deenen gizing said relay to release said switches.

12. In an automatic telephone system, a temporarily established connection including respectively, a calling subscribers line, an outgoing impulse repeater, a trunk line, anincoming repeater, automatic switches, and means at said outgoing repeater controlled by the disconnection of the calling subscriber for momentarily connecting battery and ground, respectively, to the two talking conductors of said trunk line, and

means in said incoming repeater responsive thereto to cause the release of said switches.

13. In an automatic telephone system, a temporarily established connection including, respectively, a calling line, a two conductor trunk, an incoming repeater, and a called line, a line relay in said repeater having two windings for-feeding battery and ground to the two conductors of said trunk, respectively, a second relay having contacts for normally connecting the windings of said line relay to the conductors of said trunk, means controlled by the response of the called subscriber for energizing said second relay to disconnect said line relay and battery and ground connections from the conductors of said trunk, and means controlled by the calling subscriber for deenergizing said second relay to again connect said line relay and battery and ground connections to said trunk.

14. In an automatic telephone system, a temporarily established connection including, respectively, a calling line, a trunk line, a repeater, automatic switches, and a called line, a line relay in said repeater having two windings for normally feeding battery and ground to the talking conductors of said trunk line, a second relay in said re eater, a circuit for'energizing said secon relay when the called subscriber answers to disconnect the windings of said line relay and battery and ground from the talking conductors of said trunk line, means for reducing the flow of current in said circuit, and means controlled by the calling subscriber for deenergizing saidsecond relay to release said switches.

15. In an automatic telephone system, a temporarily established connection including, respectively, a calling line, a trunk line, a repeater, automatic switches, and a called line, a line relay in said repeater having two windings for normally feeding batter and ground to the talking conductors 0 said trunk line, a differential relay in said repeater, a circuit for energizing said difi'erential relay when the called subscriber answers to disconnect the windings of said line relay and battery and ground from the talking conductors of said trunk line, and means controlled by the calling subscriber for deenergizing said diflerential relay to release. said switches.

16. In an automatic telephone system, a

.temporarily established connection includ- 7 ing, respectively, a calling line, a trunk line,

a repeater, automatic switches, and a called line, a line relay in said repeater having two windings for normally feeding battery and ground to the talking conductors of said trunk line, a differential relay in said repeater, a circuit for energizing said differential relay when the called subscriber answers to disconnect the windings of said line relay and battery and ground from the talking conductors of said trunk line, and means controlled by the calling subscriber to momentarily connect battery and ground to the talkin conductors of said trunk line to cause said differential relay to deenergize and release said switches.

17. 'In an automatic telephone system, a temporarily established connection including, respectively, a calling line, a trunk line comprising only two conductors, an incoming repeater, and a called line, a line relay in said repeater having two windings for feeding battery and ground, respectively, to the two conductors of said trunk line, a differential relay having contacts for normally connecting the windings of said line relay to the conductors of said trunk line, a back bridge relay in said repeater for feeding talking battery to the called line, an energizing circuit for said differential relay including contacts on said back bridge relay, said back bridge relay operated by the response of the called subscriber for closing said energizing circuit to cause said diiferential relay to energize and disconnect said line relay and battery and ground from the conductors of said trunk line, another circuit for said differential relay including the two conductors of said trunk line in series, and means controlled by the calling subscriber for closing said last mentioned circuit to cause said differential relay to deenergize and again connect said line relay and battery and ground connections to the conductors of'said trunk line.

18. In an automatic telephone system, a. temporarily established connection including, respectively, a calling line, a trunk line comprising only two conductors, an incoming repeater, and a called line, a line relay in said repeater having two windings for feeding battery and ground, respectively, to the two conductors of said trunk line, a differential relay having contacts for normally connecting the windings of said line relay to the conductors of said trunk line, a back bridge relay in said repeater for feeding talking battery to the called line, an energizing circuit for said differential relay including contacts on said back bridge relay, said back bridge relay operated by the response of the called subscriber for closing said energizing circuit to cause said differential relay to energize and disconnect said line relay and battery and ground from the conductors of said trunk line, a deenergizing circuit for said differential relay including the two conductors of said trunk line in series, and means independent of said contacts in said energizing circuit for preventing the reenergization of said differential relay. 7

19. In astelephone system, two exchanges, a trunk line connecting said exchanges, means for seizing said trunk line in one exchan e, a line relay in the trunk line at the secon exchange having two windings through the medium of which operating current is normally connected to the conductors of said trunk line, automatic switches in the second exchange, contacts on said relay for control ling said switches to com lete a connection, and means controlled by t e response of the called subscriber for disconnecting said rela and all battery connections from said trunk line during conversation.

20. In a telephone system, two exchanges,

a trunk line connectin said exchanges, means for seizing the trunk line in the first exno change, means for repeating impulses over said trunk line to the second exchange, a line relay in said second exchange having two windings through the medium of which operating current is normally connected to said trunk line, automatic switches in the second exchange, contacts on said line relay for re peating the impulses sent over said trunk line to operate said switches to complete a connection, a back bridge relay in said trunk line in the second exchange operated by the response of thecalled subscriber, said back bridge relay feeding talking battery to the called subscriber, and means controlled by said back bridge relay for disconnecting said line relay and all battery connections from said trunk line during conversation and for maintaining said switches in operated position independent of said line and back bridge relays and the called subscriber.

I 21. In a telephone system, two exchanges,

a trunk line connecting said exchanges, means for seizing the trunk line in the first exchange, means for repeating impulses over said trunk line to the second exchange, a line relay in said second exchange having two windings through the medium of which'operating current is normally connected to said trunk line, automatic switchesin the second exchange, contacts on said line relay for repeating the impulses sent over said trunk line to operate said switches to complete a connection, a back bridge relay in sa1d trunk line in the second exchange operated by the response of the called subscriber, said back bridge relay feeding talking battery to the called subscriber, means controlled by said back bridge relay for disconnecting said line relay and all battery connections from said trunk line during conversation and for maintaining said switches in operated position independent of said line and back bridge relays and the called subscriber, and means C011". trolled from the trunk line in the first exchange for releasing said switches.

22. In a telephone system, a trunk line com prising only two conductors, means for seizing said trunk line, an impulsing circuit 1ncluding, respectively, the two conductors of said trunk line, the two windings of a line relay, and battery and ground connections in series, automatic switches controlled by said impulse circuit to complete a connection, a talking circuit including the two conductors of said trunk line but excluding said line relay and all battery and ground connections, means controlled by the response of the called subscriber for automatically switching the conductors of said trunk line from the impulsing circuit to the talking circuit, and means controlled by the calling subscriber for connecting battery and ground to said talking circuit.

23. In an automatic telephone system, a trunk line, automatic switches, means controlled over said trunk line for operating said switches, a relay in said trunk line normally connecting battery and ground to 'the talking conductors of said trunk line, means for energizing said relay to disconnect all battery and ground connections from said trunk line, and means controlled over the talking conductors of said trunk linein" series for denergizing said relay to release said switches.

24. In an automatic telephone system, a temporarily established connection including respectively, a calling subscribers line, a two conductor trunk line, and step by step automatic switches, means controlled responsive to the calling subscriber replacing his receiver for momentarily connecting battery and ground, respectively, to the two talking conductors of said trunk line, and a relay controlled by said momentary connection of battery and ground over the two conductors masses 0t said trunk line in series to cause the re lease of said switches.

25. In an automatic telephone system, a two conductor trunk line, automatic switches, means controlled over said trunk line for op erating said switches to extend a connection, a difierential relay in said trunk line energized over a local circuit including one winding of said relay, means controlled by said relay tor maintaining said switches in operated position, and means for deenergizing said relay over a circuit including a second winding of said relay and the two conductors of said trunk line in series to cause the release of said switches.

26. In a telephone system, two exchanges, a two-way trunk line connecting said exchanges and terminating in each exchange in a dry trunk repeater, said dry trunk repeaters normally connecting battery and ground to the conductors of said trunk line, and means in said repeaters for controlling the disconnection of all battery and ground connections from the conductors of said trunk line during conversation.

27. In a telephone system, a trunk, a calling and a called line, means for extending a connection from said calling line to said called line via said trunk, means for answering the call, a relay comprising two opposing windings, means responsive to the answering of the call for closing a circuit for one winding of said relay to operate the relay, and means responsive to the calling party disconnecting for closing a circuit for the other winding of said relay whereby the relay is deactuated.

28. In a telephone system, a trunk, a calling and a called line, means including an impulsing relay bridged across the conductors of said trunk for extending a call from said calling line to said called line, a relay comprising two opposing windings, means responsive to the called party answering the call for closing a circuit for one winding of said relay whereby the relay energizes, disconnects said impulsing relay from the trunk and connects its own other winding thereto, and means responsive to the calling party disconnecting for closin a circuit for the other winding of said relay whereby the relay deactuates and releases the connection.

29. In a telephone system, anincoming trunk, an outgoing trunk, a repeating coil comprising a plurality-of windings inductively connecting said trunks, an impulsing circuit including conductors of said incoming trunk and windings of said repeating coil, a control circuit including conductors of said outgoing trunk and other windings or said repeating coil, and means responsive to the transmission of impulses over said impulsing circuit for short circuiting the windings of said repeating coil in both the impulsing and control circuits.

30. In a telephone system, an incoming trunk, a repeating coil comprising a plurality of windings, an impulsing circuit normally including windings of said repeating coil serially connected in the conductors of said 

